Lymphatic System and Innate Immunity

Overview

• Lymphatic System: Network of cells, tissues, and organs responsible for producing, maintaining, and distributing lymphocytes.
  • Lymphocytes: Include B cells and T cells, involved in specific immunity.
  • Functions: Resists infections, maintains fluid balance, transports lymphocytes, and returns interstitial fluid to the cardiovascular system.
• Lymph: Plasma-like fluid that moves through lymph vessels, originally plasma in blood, becomes interstitial fluid, then termed lymph.

Lymphatic Vessels and Organs

• Lymphatic Vessels: Carry lymph collected from tissues and return it to the bloodstream.
  • Start as lymphatic capillaries, larger and thin-walled compared to cardiovascular capillaries.
  • Lacteals in the small intestine for lipid absorption.
• Lymphatic Organs: Include spleen, thymus, lymph nodes, tonsils.
  • Organs have a capsule, while tissues like tonsils do not.
  • Lymph nodes filter lymph, produce and store lymphocytes.

Major Lymphatic Structures

• Cisterna chyli: Expanded base of the thoracic duct, collects lymph from the lower body.
• Thoracic Duct: Drains lymph from most of the body into the left subclavian vein.
• Right Lymphatic Duct: Drains lymph from the upper right quadrant into the right subclavian vein.

Innate Immunity

• Innate Defenses: Non-specific, present at birth, do not require previous exposure.
  • Physical Barriers: Skin, mucous membranes, secretions like sweat and tears.
  • Phagocytes: Neutrophils, eosinophils, macrophages that engulf pathogens.
  • Immunological Surveillance: Natural killer cells targeting infected and cancerous cells.
  • Interferons: Proteins released by virus-infected cells to alert neighboring cells.
  • Complement System: Proteins that assist antibodies in destroying pathogens.
  • Inflammatory Response: Redness, heat, swelling, pain; limits infection spread.
  • Fever: Elevated body temperature to inhibit pathogen growth and enhance immune function.

Key Concepts

• Lymphoid Tissues and Organs: Sites of lymphocyte production and filtration of lymph.
• Adaptive Immunity: Specific immunity involving B and T cells; not discussed in detail here, meant for future coverage.
• Interconnected Systems: Lymphatic and circulatory systems work together to maintain fluid balance and immune defense.

Additional Details

• Macrophages: Derived from monocytes, involved in phagocytosis, more resilient than neutrophils.
• Natural Killer Cells: Use perforins to induce cell lysis in infected or cancerous cells.
• Inflammation Signs: Redness, heat, swelling, pain to protect and heal tissues.
• Fever Function: Increases metabolic rate and inhibits pathogen reproduction.